Hippocampal-cortical interaction during sleep promotes transformation of memory for long-term storage in the cortex. In particular, hippocampal sharp-wave ripple associated neural activation is important for this transformation during slow-wave sleep. The anterior cingulate cortex, or ACC, has been shown crucial for storing such memories. However, little is known about how ACC activity is influenced by hippocampal ripple activity during sleep. We report here that the hippocampal ripple activity triggers immediate ACC neural firings. By recording from ACC and hippocampal CA1 simultaneously in mice, we found that while almost all ACC neurons showed increased activity prior to hippocampal ripple activity, a subpopulation (17%) fire immediately after ripple activity. This post-ripple activation of ACC neurons correlated positively with ripple amplitude. Moreover, the same neurons were selectively activated upon electrical stimulation of the CA1. These results suggest that hippocampal sharp-wave ripple associated activation regulates activity of a small population of ACC neurons, a process that may play a critical role in memory consolidation.